Convert list of lists into a normal list

Question

I have a list of lists:

a = [['0.06'], ['0.54'], ['0.61']]

I want to convert this list into normal list like this:

a = [0.06, 0.54, 0.61]

How can I do it it

Possible duplicate of [Making a flat list out of list of lists in Python](https://stackoverflow.com/questions/952914/making-a-flat-list-out-of-list-of-lists-in-python) — heemayl, Jan 10 '18 at 21:05
@pylang: I am sorry for that... The first comment looked *so* out of place, I decided to check the edits. The OP made it an entirely new question – which goes head on against SO rules. — Jongware, Jan 10 '18 at 22:26
I've rolled-back to the version that has existing answers. OP: if you have a different question, please post a new one. — wim, Jan 10 '18 at 22:30
Wim, good call... I guess I got distracted by looking for precedents on [meta]. @pylang: this "clever" tactic is used by people trying to avoid a question ban. Theybelieve they can ask as many questions as they want, and are not interested in helping a community at large, only themselves. One related Meta discussion (there are pages full of 'em): https://meta.stackoverflow.com/questions/265301/would-it-be-ok-to-change-a-downvoted-question-into-a-completely-different-questi — Jongware, Jan 10 '18 at 22:38
@pylang: "The edits that completely alter the question are considered **vandalism**." (Even if done by the question asker.) — Jongware, Jan 10 '18 at 22:41

score 3 · Accepted Answer · answered Jan 10 '18 at 21:03

3

Using a list comprehension:

>>> a = [['0.06'], ['0.54'], ['0.61']]
>>> [float(x) for [x] in a]
[0.06, 0.54, 0.61]

answered Jan 10 '18 at 21:03

wim

Can you explain how `[x]` works? I'm unfamiliar with transforming a value within a for statement. – pylang Jan 10 '18 at 22:21
This is binding to a `target_list` in the grammar, and is documented [here](https://docs.python.org/3/reference/compound_stmts.html#the-for-statement). – wim Jan 10 '18 at 22:26
Wow. That is a gem. Thank you. – pylang Jan 10 '18 at 22:34

score 2 · Answer 2 · answered Sep 26 '19 at 10:47

2

You can do it with zip() function (returns tuple):

list(zip(*a))[0]

Output: 
('0.06', '0.54', '0.61')

To get list instead of tuple (when you want to modify the list):

list(list(zip(*a))[0])

Output:
['0.06', '0.54', '0.61']

answered Sep 26 '19 at 10:47

Lukas

pylang · Answer 3 · 2018-01-10T22:36:11.630

1

Alternatively, using a functional approach:

list(map(lambda x: float(x[0]), a))
# [0.06, 0.54, 0.61]

Using itertools to first merge the sublists:

import itertools as it


list(map(float, it.chain.from_iterable(a)))
# [0.06, 0.54, 0.61]

A list comprehension is arguably more elegant and clever.

edited Jan 10 '18 at 22:36

answered Jan 10 '18 at 22:16

pylang

3 Answers3